There is so much discussion on what Raj said. But, all this is just the symptom. The cause is long forgotten. The mistakes committed by the first Govt of Independent India is responsible for the present situation.
1) The division of India on linguistic basis has taken just 60 years to get to each other to fight. 60 Years in a Nation's history is too short a period and the problem has already started being seen.
2) From the time of post independence, none of the Political Leaders showed that India is one country. They always said "Unity in Diversity" there by recognising the diversity and the later politicians totally used this to their own political advantage.
3) Even now, it is difficult for one to believe that we are all living in one country. Just try going from one state into another. The permits/Checkposts/Taxes etc are all there to show with sufficient proof that we are not in one country. And language is not just the issue here.
